Performance and specific emissions contours of a diesel and RME fueled compression-ignition engine throughout its operating speed and power range

Many studies presenting performance and emissions characteristics of compression-ignition (CI) engines operating with various fuels present these characteristics at a few load settings and engine rotational speed combinations. In general engine performance and emissions contours have not been investigated throughout the operating speed and power range of engines. In this paper the performance and specific emissions contours of a diesel and rapeseed methyl ester (RME) fueled CI engine are experimentally investigated, assessed, compared, and critically discussed. The contours are plotted on load (brake power) versus engine rotating speed figures throughout the engine operating range. The thermal efficiency with diesel and RME are comparable for all ranges of speeds and power outputs. At the maximum power range RME has slightly higher thermal efficiency. From the location of maximum NO_X contours in the central region of the power-speed range, any increase or decrease in either power or speed across the map shall result in lower specific NO_X. RME produces lower NO_X compared to the diesel fuel. At the higher loads RME produces fewer unburned hydrocarbon emissions than diesel, but in medium and intermediate loads the unburned hydrocarbon emissions are comparable. CO₂ is lower with RME than diesel throughout the engine operating range.